The present invention relates to a sinus conduit for a prosthetic heart valve and more particularly to a combination of such a sinus conduit and valve that may be used in artificial circulatory equipment which may be employed to assist circulation in patients with impaired heart functions.
In artificial circulatory equipment, it has been proposed that a prosthetic valve may be enclosed within a structure known as a sinus. Generally the valve will have a plurality of flexible leaflets which serve to open and close the valve to blood flow and the sinus will have a plurality of peripherally disposed lobes located around the leaflets.
There are however disadvantage with existing lobed sinuses in that the shape of the lobes tends to allow blood to accumulate therein with an attendant danger of thrombus formation.
The present invention seeks to obviate or mitigate this disadvantage.
According to the present invention there is provided the combination of
(a) a prosthetic valve having a plurality of flexible leaflets for opening and closing the valve and each having an edge region attached to a frame of the valve and further having a free edge, and
(b) a sinus having a plurality of lobes symmetrically disposed around the periphery of the sinus, and a conduit (the downstream conduit) located downstream of said lobes in the direction of blood flow through the sinus, the sinus being such that the valve may be located therein with said attached edges of any one of the leaflets extending in coincidence with an upstream edge region of a respective lobe, wherein in axial section taken centrally through a lobe
(i) the angle of intersection (xcex3) of each leaflet with its respective lobe is from 165 to 195xc2x0,
(ii) the radius of curvature of the lobe increases continuously to the downstream end thereof,
(iii) at said downstream end the angle (xcfx89) between notional projection of the inner surface of the lobe into the downstream conduit and the surface of said conduit is 23-37xc2x0, and
(iv) the volume of Rswp/Rttl (as hereinbefore described) is at least 0.14.
The above defined criteria (i)-(iii) of the lobe ensure that there is continuous movement of blood within the lobe to prevent areas of stagnation and ensure washing of the valve leaflets. More particularly, feature (i) ensures that there is no stagnation of the intersection of the leaflet and the sinus whereas feature (iii) ensures that a portion of the blood issuing as a xe2x80x9cjetxe2x80x9d from the valve (at least beyond a certain degree of opening thereof) is able to be xe2x80x9cdeflectedxe2x80x9d for recirculating motion within the lobe.
Preferably the valve has three leaflets and the sinus is of tri-lobed structure. The valve is preferably of the type disclosed in WO-A-9318721 (The University of Leeds).
The sinus may be of a flexible material, e.g. a biocompatible polyurethane.
Preferably the sinus further comprises an upstream conduit whereby said lobes are located between said upstream and downstream conduits. For preference the internal diameter of the upstream conduit is greater than that of the downstream conduit.